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Fix quadratic interpolation

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Johannes Schönberger
2014-08-31 13:30:33 -04:00
parent 84871a6d6f
commit 8753979fd2
1 changed files with 31 additions and 36 deletions
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skimage/_shared/interpolation.pxd
+31 -36
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@@ -64,12 +64,12 @@ cdef inline double bilinear_interpolation(double* image, Py_ssize_t rows,
"""
cdef double dr, dc
cdef Py_ssize_t minr, minc, maxr, maxc
cdef long minr, minc, maxr, maxc
minr = <Py_ssize_t>floor(r)
minc = <Py_ssize_t>floor(c)
maxr = <Py_ssize_t>ceil(r)
maxc = <Py_ssize_t>ceil(c)
minr = <long>floor(r)
minc = <long>floor(c)
maxr = <long>ceil(r)
maxc = <long>ceil(c)
dr = r - minr
dc = c - minc
top = (1 - dc) * get_pixel2d(image, rows, cols, minr, minc, mode, cval) \
@@ -86,9 +86,9 @@ cdef inline double quadratic_interpolation(double x, double[3] f):
Parameters
----------
x : double
Position in the interval [-1, 1].
f : double[4]
Function values at positions [-1, 0, 1].
Position in the interval [0, 2].
f : double[3]
Function values at positions [0, 2].
Returns
-------
@@ -96,7 +96,9 @@ cdef inline double quadratic_interpolation(double x, double[3] f):
Interpolated value.
"""
return f[1] - 0.25 * (f[0] - f[2]) * x
return (x * f[2] * (x - 1)) / 2 - \
x * f[1] * (x - 2) + \
(f[0] * (x - 1) * (x - 2)) / 2
cdef inline double biquadratic_interpolation(double* image, Py_ssize_t rows,
@@ -124,24 +126,17 @@ cdef inline double biquadratic_interpolation(double* image, Py_ssize_t rows,
"""
cdef Py_ssize_t r0 = round(r)
cdef Py_ssize_t c0 = round(c)
if r < 0:
r0 -= 1
if c < 0:
c0 -= 1
# scale position to range [-1, 1]
cdef double xr = (r - r0) - 1
cdef double xc = (c - c0) - 1
if r == r0:
xr += 1
if c == c0:
xc += 1
cdef long r0 = <long>round(r) - 1
cdef long c0 = <long>round(c) - 1
# scale position to range [0, 2]
cdef double xr = r - r0
cdef double xc = c - c0
cdef double fc[3]
cdef double fr[3]
cdef Py_ssize_t pr, pc
cdef long pr, pc
# row-wise cubic interpolation
for pr in range(r0, r0 + 3):
@@ -210,20 +205,20 @@ cdef inline double bicubic_interpolation(double* image, Py_ssize_t rows,
"""
cdef Py_ssize_t r0 = <Py_ssize_t>r - 1
cdef Py_ssize_t c0 = <Py_ssize_t>c - 1
if r < 0:
r0 -= 1
if c < 0:
c0 -= 1
cdef long r0 = <long>floor(r)
cdef long c0 = <long>floor(c)
# scale position to range [0, 1]
cdef double xr = r - floor(r)
cdef double xc = c - floor(c)
cdef double xr = r - r0
cdef double xc = c - c0
r0 -= 1
c0 -= 1
cdef double fc[4]
cdef double fr[4]
cdef Py_ssize_t pr, pc
cdef long pr, pc
# row-wise cubic interpolation
for pr in range(r0, r0 + 4):
@@ -236,7 +231,7 @@ cdef inline double bicubic_interpolation(double* image, Py_ssize_t rows,
cdef inline double get_pixel2d(double* image, Py_ssize_t rows, Py_ssize_t cols,
Py_ssize_t r, Py_ssize_t c, char mode,
long r, long c, char mode,
double cval):
"""Get a pixel from the image, taking wrapping mode into consideration.
@@ -269,8 +264,8 @@ cdef inline double get_pixel2d(double* image, Py_ssize_t rows, Py_ssize_t cols,
cdef inline double get_pixel3d(double* image, Py_ssize_t rows, Py_ssize_t cols,
Py_ssize_t dims, Py_ssize_t r, Py_ssize_t c,
Py_ssize_t d, char mode, double cval):
Py_ssize_t dims, long r, long c,
long d, char mode, double cval):
"""Get a pixel from the image, taking wrapping mode into consideration.
Parameters
@@ -303,7 +298,7 @@ cdef inline double get_pixel3d(double* image, Py_ssize_t rows, Py_ssize_t cols,
+ coord_map(dims, d, mode)]
cdef inline Py_ssize_t coord_map(Py_ssize_t dim, Py_ssize_t coord, char mode):
cdef inline Py_ssize_t coord_map(Py_ssize_t dim, long coord, char mode):
"""Wrap a coordinate, according to a given mode.
Parameters